Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Abstract

Background

Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent impact on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. This is uniquely useful following the COVID-19 pandemic and for other large-scale mortality shocks in the future. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of mortality globally and over time, providing a more nuanced understanding of their impact on global populations.

Methods

The GBD 2021 cause of death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 through 2021. The analysis used 56 604 total sources of data, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model (CODEm)—a modelling tool developed for GBD to evaluate the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific fatal burden estimates—with alternative strategies adapted to model causes with very limited data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2.5th and 97.5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We used the coefficient of variation and the fraction of population affected by 90% of deaths, to highlight concentrations of mortality that may inform cause-specific policy-relevant insights. Findings are reported in counts and age-standardised rates. Methodological improvements for cause of death estimates in GBD 2021 include the expansion of under-5 ages to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of pandemic-specific mortality from COVID-19 and “other pandemic-related mortality” (OPRM)—which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis causes. For this analysis, 199 new country-years of vital registration cause of death data, five country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds.

Findings

The leading causes of age-standardised deaths globally were the same in 2019 as in 1990; these were, in descending order, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94.0 deaths (95% UI 89.2–100.0) per 100 000. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke and chronic obstructive pulmonary disease to the third and fourth places, respectively. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271.0 deaths [250.1–290.7] per 100 000) and Latin America and the Caribbean (195.4 deaths [182.1–211.4] per 100 000). The lowest age-standardised death rates from COVID-19 were observed in the high-income super-region (48.1 deaths [47.4–48.8] per 100 000) and southeast Asia, east Asia, and Oceania (23.2 deaths [16.3–37.2] per 100 000). Globally, trends in life expectancy showed steady improvements between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy demonstrates the positive impact that reductions in enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others, have contributed to increased survival. Despite these improvements in causes of death until 2019, a net drop of 1.6 years occurred in global life expectancy between 2019 and 2021, primarily due to elevated death rates due to COVID-19 and OPRM. Examining the impact of COVID-19 on life expectancy between 2019–2021 is crucial because each of the seven GBD super-regions showed an overall improvement from 1990 to 2021, obscuring the negative impact on life expectancy isolated in the years of pandemic. There was high variability between super-regions, with southeast Asia, east Asia, and Oceania gaining 8.3 years (6.7–9.9) of life expectancy overall, while displaying the smallest reduction in life expectancy due to COVID-19 of 0.4 years. The largest decline in life expectancy due to COVID-19 occurred in Latin America and the Caribbean, which lost 3.6 years. In addition, we found that 53 of the 288 causes of death were highly concentrated in locations that contained less than 50% of the global population as of 2021, and that these causes of death became progressively more concentrated since 1990, when only 44 of 288 showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles.

Interpretation

Longstanding gains in life expectancy and reductions in many of the leading causes of death have been disrupted by COVID-19, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period, with the biggest gains attributed to reductions in mortality due to enteric infections, lower respiratory infections, stroke, and neonatal deaths. Our findings about regional variation driving increases in life expectancy have clear policy utility, as does our analysis of changing mortality trends. Deaths from enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, measles, and other causes that were once widespread globally are now increasingly concentrated. The changes to mortality concentration reveal marked regional differences in public health success, which alongside further investigation of changing risks, interventions, and relevant policy, provides an important opportunity to better understand how to reduce mortality. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. The pandemic highlighted inequities in existing health systems as well as health system preparedness, both of which were highly heterogenous globally in terms of population mortality outcomes. This has rightly prompted new calls for increasing equity in pandemic preparedness alongside calls for strengthening existing health systems.

Funding
Bill & Melinda Gates Foundation.

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Identifiers

ORCID for Samuele Cortese: orcid.org/0000-0001-5877-8075

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